1. Field of the Invention
The present invention generally relates to a dedicated short-range communication apparatus (DSRC apparatus) destined to be mounted on an automobile or motor vehicle (hereinafter also referred to as the on-vehicle DSRC apparatus) which can be employed in an electric toll collection system (also referred to as the ETC system) of an intelligent transport system (also referred to as the ITS system). In particular, the present invention is concerned with an on-vehicle DSRC apparatus which can positively ensure a given or predetermined area for communication by automatically holding an antenna array constantly at a proper angle relative to the horizontal plane notwithstanding the locations of the motor vehicle (such as a windshield, a dashboard or the like) at which the on-vehicle DSRC apparatus is to be installed have different angles relative to the horizontal plane.
2. Description of Related Art
In recent years, in the field of the on-vehicle DSRC apparatus designed for performing transmission/reception of information with equipment installed on a road (hereinafter also referred to as the on-road equipment), there have been reported various proposals concerning a variety of improvements of the on-vehicle DSRC apparatus in an effort to making proper the angle at which the antenna array is positioned or installed.
In the conventional on-vehicle DSRC apparatus known heretofore, the antenna array is adjusted to a preset proper angle by means of a motor driver when the antenna array through which communication is performed is mounted on the motor vehicle on a predetermined location thereof. (For particulars, reference may have to be made to Japanese Patent Application Laid-Open Publication No. 14019/1995 (JP-A-H7-14019)).
As is apparent from the above, the conventional on-vehicle DSRC apparatus suffers a problem that the motor driver is required for adjusting the angle of the antenna array to a proper value when the on-vehicle DSRC apparatus is mounted, which involves high cost.